<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .div1 {
            height: 100px;
            background-color: cadetblue;
        }

        .div2 {
            width: 100px;
            height: 1000px;
            background-color: red;
            display: none;
            float: right;
            /* font-size: 0; */
            -webkit-text-size-adjust: none;
        }

        a {
            width: 100px;
            height: 100px;
            background-color: green;
            display: inline-block;
            /* font-size: 0; */
            -webkit-text-size-adjust: none;
        }
        .div1:hover .div2{
            display: block;
        }
    </style>
</head>

<body>
    <div class="div1">
        <div class="div2"></div>
    </div>
    <div class="div2"></div>
    <a href="">2123</a>
</body>

</html>